1. Field of the Invention: The invention relates to sewing machine hooks including a hook beak for seizing loops of needle thread during the formation of lock stitches.
2. Description of the Prior Art: It is well known to provide a sewing machine hook with a hook beak which can be adjusted by an operator so as to position it relative to a needle and thereby avoid having the hook beak engage and break the needle. It is also known to provide a sewing machine hook with a needle guard effective during rotation of the hook to engage a needle which may be in the path of rotation of the hook beak and bend the needle out of the way of the hook beak to avoid contact between the two and consequent damage to the needle or hook beak.
In arrangements requiring the operator to position the hook beak so as to avoid interference with a needle there is always the possibility of the hook beak coming dislodged from its adjusted position. Furthermore, the operator is inconvenienced by having to concern himself with adjustments to the hook beak. Also, if the operator should forget to adjust the hook beak, as for example when a new needle of a greater diameter than a previously used needle is inserted in the machine, damage to the new needle or the hook beak, or to both may insue. The use of a needle guard which serves to bend a needle out of the way of a hook beak has disadvantages in that repeated flexing of the needle may result in fatigue failure causing the needle to snap.
It is a prime object of this invention to provide a sewing machine hook with an improved arrangement which functions automatically to prevent interference between a needle and hook beak, which does not require adjustment by an operator, and which avoids the necessity of bending the needle away from the hook beak.